At present, the data rates of digital signal transmissions may reach values such that spectrum components thereof reach the microwave range.
In order to conserve the waveform of the transmitted signals, it is essential to use perfectly matched transmission media since the slightest non-matched connection can be catastrophic from the transmission point of view.
At very high data rates, e.g. about 100 Mbit/s and above, the maximum length that can be tolerated for a branch line connected to a bus is very short, and a function of the data rate; the higher the data rate, the shorter the maximum length. For example, at a data rate of 100 Mbit/s, each branch line on a bus cannot be more than a few centimeters long since even when terminated with its characteristic impedance, it nevertheless gives rise to a degree of mismatch on the bus. If longer than 5 centimeters, a branch line gives rise to a non-acceptable degree of disturbance to the digital signals it transmits.
In the very common situation of distributing very high data rate digital signals to electronic devices mounted on a common printed circuit card, this limited line length imposes severe constraints on the locations that the electronic devices may occupy on the card, and these constraints may limit the number of electronic devices that can be placed on the card to one or two, even though there is room on the card for more devices.
The object of the invention is to make it possible to distribute very high data rate digital signals without disturbance via lines branching from a bus.
Another object of the invention is to avoid constraints on the location of electronic devices on a given printed circuit card, which constraints are due to the very short lengths of branch lines.